This section is intended to provide a background or context to the invention that is recited in the claims. The description herein may include concepts that could be pursued, but are not necessarily ones that have been previously conceived or pursued. Therefore, unless otherwise indicated herein, what is described in this section is not prior art to the description and claims in this application and is not admitted to be prior art by inclusion in this section.
The following abbreviations that may be found in the specification and/or the drawing figures are defined as follows:                3GPP third generation partnership project        ACCS autonomous component carrier selection        BIM background interference matrix        C/I carrier interference ratio        DL downlink (eNB to UE)        eNB Node B/base station of an LTE system        LTE long term evolution (evolved UTRAN)        MM/MME mobility management/mobility management entity        UL uplink (UE to eNB)        UTRAN universal terrestrial radio access network        
Heterogeneous networking (HetNet) involves the use of smaller cells/access nodes operating in functional cooperation with conventional macro (cellular) cells/access nodes and in overlapping geographical and frequency space. Adjacent cells cooperate to achieve more efficient use of scarce radio resources even if they are different wireless systems. Such smaller cells may variously be termed micro cells, pico cells, femto cells and home eNBs. For example, there may be femto-cells, sometimes termed home base stations HeNBs operating over a very limited geographic area, existing side by side with other femto-cells and with traditional network-operated cellular base stations/eNBs. These femto cells may cooperate to mitigate interference with one another, or at least to positively limit their own interference to adjacent cells to avoid the greedy cell scenario in which one cell occupies more bandwidth resources than its traffic justifies, at the expense of an adjacent cell.
The generalized HetNet concept is shown at FIG. 1A. At the left are illustrated conventional or macro eNBs 101-103 each covering idealized hexagonal cell boundaries, and at the right is the expanded inset additionally showing femto cells 120-123. Typically the femto cells operate over a smaller geographic area than the macro cells but due to proximity to cell edges their communications may interfere with one or more macro cells as well as one or more femto cells. By example, transmissions to or from femto access node 121 may interfere with macro eNB 103 and femto access node 123 despite both of those lying in the neighboring macro cell.
FIG. 1B illustrates the concept of carrier aggregation CA in LTE Release 10. The whole system bandwidth (e.g., 100 MHz) is divided into a plurality of component carriers CCs. Each macro eNB will have one CC as primary and may take other CCs into use in the cell given its traffic conditions. Such other CCs are termed secondary or extension CCs, and may or may not be backward compatible with legacy UEs which operate in the LTE Release 8/9 systems. If the femto HeNBs are also to employ the CA concept, it is expected they also will have one primary CC and potentially additional secondary/extension CCs as their own traffic needs dictate.
It is anticipated that each femto cell will maintain a background interference matrix (BIM) which expresses the interference coupling with surrounding cells. Details of the BIM concept may be seen at document R1-090235 by Nokia and Nokia Siemens Networks entitled: USE OF BACKGROUND INTERFERENCE MATRIX FOR AUTONOMOUS COMPONENT CARRIER SELECTION FOR LTE-ADVANCED (3GPP TSG RAN WG1 #55-bis Meeting; Ljubljana, Slovenia; 12-16 Jan. 2009), as well as at co-owned U.S. patent application Ser. No. 13/036,464 entitled ENHANCED ESTIMATION OF UPLINK INTERFERENCE COUPLING (filed on 28 Feb. 2011). The BIM is built locally by each eNB based on measurements from the user terminals that are served by that same eNB. Depending on the BIM and the offered traffic per cell, each eNB will autonomously select the component carriers it needs, while at the same time ensuring that it does not create excessive interference in the surrounding eNBs. The BIM can also be used to ensure that the performance in the host cell (macro eNB) is acceptable.
There is an autonomous component carrier selection scheme ACCS which the femto eNBs are to use for interference management, and the ACCS instructs the eNBs how to construct and how to utilize the BIMs. The ACCS is detailed more fully at a paper by L. Garcia, K. I. Pedersen, P. E. Mogensen entitled AUTONOMOUS COMPONENT CARRIER SELECTION: INTERFERENCE MANAGEMENT IN LOCAL AREA ENVIRONMENTS FOR LTE-ADVANCED (IEEE Communications Magazine, September 2009). To optimize system performance utilizing the ACCS and the BIM concepts in local area environments must take into account the dense deployment of low power eNBs such as the femto cells/HeNBs noted above in such local environments.
One important distinction of neighboring femto eNBs as compared to neighboring macro eNBs is that the dedicated X2 interface which interconnects the macro eNBs is fully under control of the same operator. Additionally, there are relatively few macro eNB manufacturers and so interoperability issues are more readily resolved. Such homogeneity may not be present in the HetNet environment. There, the different access nodes may be from many different manufacturers and operating under control of different operators or no centralized operator at all, and so an information exchange or other cooperation among them is decentralized rather than hierarchical and the communication interfaces between a group of neighboring femto eNBs may not be under control of any single operator. As a consequence one HeNB has little or no assurance that the BIM it receives from a neighbor HeNB is ‘good’, and the quality of the data in the different BIMs a given HeNB receives from multiple neighbor HeNBs may vary widely.
The emergence of decentralized packet switched cellular networks therefore introduces a new communication paradigm for network-level and even device-level (e.g., direct device-to-device communications) coordination, and this decentralization trend is expected to continue. Decisions made on collected information can no longer assume the reliability of the information, nor can it be assumed that similar-type information collected from different sources has equal reliability. This impacts the quality of the decisions themselves, such as the decision based on the BIMs received from neighbor cells whether to take a secondary/extension CC into use. These teachings address the above changing paradigm by providing a means by which various communicating entities can assess data reliability (e.g., genuineness or accuracy) more individually rather than rely on assumptions which are invalid for a non-hierarchical wireless communication system.